Mitsunari confided a plan to raise an army for the subjugation of Ieyasu to Nagamori Mashita and Ekei Ankokuji, a military monk of the Mori clan.
And, on July 12, Mitsunari held a meeting with Yoshitugu, Ekei and Nagamori at SawaYama Castle.
At the meeting, “Mitsunari asked the great daimyo Terumoto Mori, who was next to Ieyasu, to accept the office of
commander-in-chief of the WESTERN ARMY, and to detain many generals who were going to participate in the Aizu subjugation forces.
Also to forbid the children and wives of the daimyos, who had conquered the east in the Uesugi conquest, to return home
and to select some hostage.”
On July 12 Terumoto Mori took office. Then five days later, he entered Osaka Castle, and became the commander-in-chief
of the WESTERN ARMY.
On the same day, three magistrates Geni Maeda, Masaie Natsuka, and Nagamori Mashita sent a manifesto to the daimyos of
Kansai. It said “Although Hideyoshi was asking us to take care of Hideyori until just before his death, Ieyasu has already begun to do as he pleases. If you do not forget favor of Hideyoshi,
I will want you to exert loyalty to Hideyori.”
Following the manifesto, Hidemoto Mori, Hideie Ukita, Hideaki Kobayakawa, Konishi Yukinaga, Yoshihiro Shimazu, and
Toyohisa Shimazu with a large number of generals, gathered, a military power approximately 100,000 soldiers.
The WESTERN ARMY compared favorably with the EASTERN ARMY. But in reality, there were a lot of daimyos in the EATERN
ARMY who belonged to the WESTERN ARMY
For example Ieyasu asked Yoshihiro Shimazu and Toyohisa Shimazu to take Fushimi Castle. They went to Mototada Torii,
who was entrenched in Fushimi Castle, and asked for entrance into the castle, which was rejected, therefore they joined the WESTERN ARMY.
Hideaki Kobayakawa communicated secretly with Nagamasa Kuroda of the EASTERN ARMY , Yasuharu Wakisaka also communicated
secretly with Takatora Todo.
In addition, the important of Terumoto Mori was divided into Hiroie Kikkawa of the Ieyasu group and Ekei Ankokuji of
the Mitsunari group and affiliations became complicated.
Shigekatsu Maeda, Katsushige Nabeshima and others were going to participate in the Aizu subjugation forces. They gave
it up because Mitsunari established the barrier in Echigawa, and so they participated in the WESTERN ARMY.
However, the hostage missions ended in failure. Many generals' wives and children escaped from Osaka Castle and Fushimi
Castle, before they were taken to Osaka Castle.
Tadaoki's wife Gracia refused to become a hostage. When Gracia prepared to commit suicide, one chief retainer, who
served as suicide assistant, set off an explosive in the residence. The hostage operation failed because of this fierce incident.